I’m not really the early-adopter type, and my own motivation is very much about producing stuff, i.e. content, rather than being at the bleeding edge of technological innovation, so I generally prefer to let technologies mature a bit before jumping in.

I’m not exactly a Linux noob anymore and certainly not a programming noob but have yet to take the plunge with RaspPi.

The oft-repeated price tag of $24 is a little misleading, of course, as there are a few other elements needed to make it an actual working unit. I’m not having a go by any means but the entry price need to include power supply, optional case, cabling and storage. The revised model “B” now has 512Mb RAM and is the only model I am interested in as the model “A” does not have Ethernet and that is one of the most compelling reasons for implementing FMTV with the RaspPi.

To recap after the Missing Link hiatus, what I was originally trying to make was a self-contained box to control and synchronise CHDK-hacked cameras for the purpose of capturing timelapse video and/or stills.

The TCP/IP interfacing was by far the most difficult aspect, and when the RaspPi popped up it seemed like a much option as a general purpose controller as it can be programmed at a much higher level with Linux which also makes it easily networkable and reprogrammable in-situ.

The downside is the cost, but only when compared with my original bare-bones design, and that never came to fruition as originally conceived.

On Amazon UK my basket came to £99.63 with Model B 512Mb, power supply, plastic case, HDMI cable, pre-loaded Raspbian “Wheezy” on 16Gb SDHC card, camera module, rubbery USB keyboard & USB WiFi adaptor. This is for a fairly complete kit of parts with which to experiment and a conceivable FMTV “module” probably could be configured for half that cost. I’ll post more about this once I have my first one up and running. I can’t choose the cheaper and smaller model A as it does not have Ethernet and my ideal configuration includes a networkable interface that can be addressed remotely for capturing over a network and/or remote control. For just the Model B (£31.19) and power supply (£3.50) with no case and a 8Gb card (£8.75), it comes in at a minimum total of £43.44.

I never did get to a manufacturing cost estimate for the original microcontroller-based design but, although it would have been a lot less, the additional functionality and convenience makes RaspPi compelling especially as I am not an electronics engineer and the circuit design was way out of my comfort zone.

So, why the camera when I’m already using CHDK-hacked still cameras? Well, it appears to be a relatively high-quality mobile phone camera and if it’s anything like the iPhone 4s camera, a pretty good wide angle camera that could be very good for timelapse capture.

OK, the FMTV Missing Link research and development has been rendered entirely redundant by the arrival of Raspberry Pi. There is simply no compelling reason to implement it with anything else, most persuasively because RaspPi has TCP/IP, and that is the the single most difficult thing to implement for someone who is not an electronics engineer.

Unless you’ve been living under a rock for the past year, you will no doubt be aware of the arrival of Raspberry Pi, a Linux-capable, credit-card-sized PC that ships for £31.86 (inc VAT & carriage). It has USB, SDHC, composite video, HMDI and ethernet, and will even run on batteries.

The fact that it is a full PC (700MHz ARM processor with FPU & GPU) means that it can be programmed with existing Linux libraries, be synchronized over IP and do local processing before passing the media to a remote location.

Still from movie trailer of "The Creature from the Black Lagoon" (1954) on Archive.org

Having finally gathered the correct bits and pieces, I’ve started putting circuits together. The basic circuit for an external time-lapse trigger is very simple and requires almost nothing more than the basic PICAXE 08M board with battery or DC power and a USB cable to connect to a CHDK-enabled camera.
If you wanted to make a very small external trigger box you could mount a coin-cell holder on the proto board and make a self-contained, battery-powered unit rather like the Gentles GentSTEREO box.
Interface circuitry to drive an infrared LED is no more than driving a normal LED but serial commands only operate on pin 0 of the PICAXE 08M, which is also used for programming the chip, so a switch needs to be included if re-programming is to be allowed.
My receiver set up doesn’t work yet and I need to check the rather clunky breadboard job I’ve constructed. I *think* I am very near to making and actual working pair of transmitter /receiver boxes. The circuitry is actually very simple and cheap to manufacture. Apart from the power supply, the Missing Link unit can be manufactured very small.
I am still having some problems with CHDK / PowerShot cameras. Using an external trigger allows autofocus lock (AFL) and autoexposure lock (AEL) to work but turning the screen off (in order to prolong the battery life) seems to exit both AFL and AEL. In which case I’m not much better off unless I use external batteries or mains power supplies.
After experimenting with an external battery box containing 3 x NIMH rechargeable batteries (3 x 1.2v = 3.6v) the camera complains and tells me to change the batteries. The stated power requirement is 3.15v. Does it really need to be that accurate? Well it appears so.
It turns out that when I test them, the NIMHs I have knock out over 1.3V each and I’m getting a little over 4.1V from 3 of them, not enough juice from 2 and too much from 3.
I built a simple voltage regulator circuit using the ubiquitous LM317 and information from National Semiconductor.http://www.national.com/ds/LM/LM117.pdfI’m getting 3.2V from my regulator but forgot the cannibalized connector cableso will have to let you know about that. I’d like to use large capacity external batteries so that I can get more life than from 2 high capacity AAs in situations where I don’t want or can’t use mains power. I’d like to make these as small as possible and hope to use a combination of pre-charged batteries and solar charging set-ups.

Having finally ordered the USB programming cable, so that I can program the PICAXE circuits from my MacBook, I get around to actually trying out the PICAXE. I started with an old prototype board that I built a few years ago.

Even after some time of trying I cannot get the the PICAXE chips to run the program even though it appears to be accepting it ok.

The instructions are a little ambiguous too. There is a document online that tells you how to install the driver for the USB programming cable.

I followed the instructions on page 14 but on my MacBook running Mc OS X 10.5.8 the options to enable the new USB device was not available. I was able to examine the /dev directory and find the entry

/ d e v / t t y . u s b s e r i a l – x x x x x x x x

After giving up on the downloaded instructions, I looked through the MacAXEpad software and found under View > Options… a place to enter the number found in the /dev directory.

It worked no problem after that, but it is not in the instructions.

However, although I have been able to download programs, I have not been able to get them to run downloaded from the MacBook. So, I went to my backup, which is a Toshiba 230CXdating from some time in the 1990’s. I had used this previously and it still works fine, so in the interest of getting on with stuff I’m using that and will try and fix the Mac link later.

So, I tried using the prototype board I’ve used before. I tested the output from the Gentles GentSTEREOPro, which sends out a pulse of 5.1v to trigger the cameras. I tested the post-resistor value on my old PICAXE circuit which gives 2.5v and this was not enough to trigger the camera. If I take a voltage before the resistor I get 3.5v and this is enough to trigger the camera. So, I did a clunky rewrite of the software to switch on an off.

This is an unedited still from a Canon PowerShot A560 at full resolution (3072 x 2304) and maximum quality – 1/10 second, f2.6, ISO 80. I’m also investigating the pay off in terms of ISO number versus shutter speed. Timelapse enabled with the Canon Hack Development Kit (CHDK).

I’ve updated the blog and created some new pages to separate some of the info into a more readable form.
I’m still a bit behind with the actual physical building of the prototypes but I will start building seriously next week. I have updated the calendar of dates I’ll be in Access Space and there will be other dates added later.
Image from “The Dinosaur and the Missing Link, A Prehistoric Tragedy” (1917), courtesy of Archive.org.

Here are 3 short timelapse videos made from the random shooting I did on day 3 of my Research & Development Bursary period at Access Space in Sheffield, UK.

I mounted 3 unsynchronized cameras in the same position but looking in different directions, all running the Canon Hack Development Kit (CHDK) to enable time-lapse shooting on Canon PowerShot cameras.
All the audio is from the Linux Open Source Sound (L.O.S.S.) project, launched in 2005 by Access Space.
Also in the picture are Bill Best, Technical Operations Manager at The Community Media Association and musician Laurence Alexander.loss.access-space.orgcommedia.org.uk